Refrigerating apparatus



R. R. CANDOR REFRIGERATING APPARATUS Oct. 4, 1938.

Filed NOV. 50, 1934 INVENTOK ATTORNEY.

PATENT OFFICE l REFRIGERATING APPARATUS Robert It. Candor, Dayton, V`Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application November 30, 1934,'Serial No. 755,329

Claims.

This inventionrelates to refrigerating apparatus and more particularly of the compressorcondenser-iixed restrictor-evaporator type.

In the copending application of Andrew A. Kucher, Serial No. 599,239, filed March 16, 1932, there is disclosed a refrigerating apparatus, vthe design of which is such thatthe -apparatus may be operated continually throughout a givenrange of loads and the refrigeration output will be the restrictor and which varlesunder different conditions of operation is the pressure difference across the restrictor. While it is possible to produce a iixed restrictor refrigerating apparatus which is inherently self-controlling as explained in the aforementioned application throughout substantially the entire range of room temperatures normally encountered, the wide variation in both head pressures and back pressures existing in thesystem between the maximum and minimum load conditions results in operation of `the system at rather Vlow efficiencies under some conditions; Since for any given system, there is a certain optimum value of head pressure and back pressure at which the system will operate at maximum efficiency, any variations from this value results in less efficient operation. Naturally, the wider the variation' in head or back pressure, the greater is the departure from maximum eiliciency, and the lower is the average efliciency over a given period.

It is an object of' the present invention, therefore, to provide a novel method and apparatus for controlling' the rate of ow of refrigerant through a xed restrictor and to thus provide smaller variations in the vhead and back pressures of the system for a given variation in output of the system.

It is a further object to provide a refrlgerating `apparatus which is self-controlling in its output throughout a substantial range of load requirement and in which the average efdciency of operation is materially increased.

Another object is toprovide a novel evaporator construction for a refrigerating apparatus having a xed restrictor associated therewith to have a variable rate of heat interchange between` the restrictor and the refrigerant in the evaporator.

Further objects and advantages of the present 5 invention will be apparent from the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present invention is clearly shown.

In the drawing:

Fig. 1 is a diagrammatic view of a refrigerating apparatus embodying thepresent invention, portions of the apparatus being broken away to show its interior construction; l

Fig. 2 is a diagrammatic view of the refrigerat- 16 ing apparatus'illustrating the levels of liquid refrigerant therein under high load conditions;

Fig. 3 is a diagrammatic view of the refrigeratng apparatus illustrating the levels of liquid refrigerant therein under low load conditions; and 20 Fig. 4 is a fragmentary View partly in cross section of a modified form of evaporator embodying the present invention.

Referring now to Fig. 1, there is shown a refrigerating apparatus comprising a motor-com- 25 pressor `unit Il) having an outlet I2 communicating with the condenser I4 by means of a conduit I6. 'I'he condenser Il communicates at its bottom portion by means of a conduit I8 with a iixed restrictor 20, which, in turn, communicatespwith 30 an evaporator 22. A conduit 24 connects 'the outlet of the evaporator with the inlet 26 of the compressor I0. In order to provide for intermittently operating the apparatus under certain conditions,v a control switch 28 isV provided for `35 opening and closing the circuit to the motorcompressor unit Ill in response to cabinet temperatures, suitable motor'starting control means 30 being provided intermediate .the switch 28 and the motor-compressor unit l0.-

The design of the various portions of the refrigerating apparatus is preferably that described in the copending application referred to previously, although it will be understood that the invention herein described may be utilized with varying 45 degrees of advantage in other" designs of apparatus. According to the embodiment illustrated, the condenser Il and the evaporator 22 are both formed of metal sheets having corrugations orl other deformations therein to provide, when the 50 sheets have been suitably welded or otherwise secured together, refrigerant passages therebetween of suitable shape.` The condenser i4 may l' include an upper header 32 for distributing compressed refrigerait across its full width and a 55 lower header 34 for collecting liquefied refrigerant. The evaporator 22 is formed into a general U shape to provide a sharp freezing zone for the freezing of water or other substances to be frozen and includes one or more horizontal shelves 3l which are formed with refrigerant passages therein to facilitate the rapid freezing of articles placed thereon. The outer vertical walls of the evaporator may be utilized for cooling the air or other circulating medium in a refrigerator cabinet to be cooled. One of the vertical walls of the evaporator 22 is formed with a bulged portion 40 within which the restrlctor 20 is mounted. The vertical location of the bulged portion 40 is such that it lies intermediate the upper and lower limitations of travel of the liquid refrigerant level in the evaporator 22.

Assuming the apparatus illustrated has been designed in accordance with the copending application above referred to, it will be seen that the compressor I0 will run continuously under all loads above a certain low limit. The setting of the control switch is such that under load conditions below this limit, the apparatus will koperate intermittently. When the compressor is running, refrigerant will be drawn from the evaporator through the conduit 24 and compressed by the compressor to be delivered through conduit I6 to the condenser I4. The liquid refrigerant condensed in the condenser I4 is delivered through the conduit I8 to the xed restrictor 20 whence it is expanded into the evaporator 22 entering the shelves at the shelf 38. Under conditions of high load, such as for example, when the room temperature within which the refrigerating apparatus is operating is rather high, refrigerant will be delivered to the evaporator at a rather fast rate, due to the high head pressure existing in the condenser at high room temperatures. Consequently, liquid refrigerant will tend to accumulate in the evaporator 22 to some such level as that indicated at 42. Inasmuch as the level 42 is above the restrlctor 20, the restrlctor will bein direct contact with the liquid refrigerant in the evaporator 22. Since the liquid refrigerant entering the restrlctor 2li is considerably warmer than the liquid refrigerant in the evaporator 22,. Y heat will be transferred from the refrigerant in the restrlctor to the refrigerant in the evaporator. Under high load conditions, with the refrigerator functioning as illustrated in Fig. 2, the heat exchange conditions between the restrlctor and the liquid refrigerant in the evaporator are at their best, due to the surrounding of the restrlctor with liquid refrigerant. Likewise, since the restrictor is surrounded with liquid refrigerant, the tendency of the refrigerant passingthrough the restrictor to gasify before leaving the restrlctor is substantially eliminated, resulting in the delivery of practically pure Iliquid refrigerant from the restrlctor 20.

Under conditions of low load, for example, on a cool day, the refrigerant is Adelivered to the evaporator at a lesser rate than on a warm day, resulting in the lowering` of the level of liquid refrigerant in the evaporator to a point such as 44 shown in Fig. 3 which is below the restrlctor 20. Under these conditions, the restrlctor 20 is surrounded with gaseous refrigerant and not only is the heat exchange factor thereby reduced, but also since therestrictor is surrounded by gaseous refrigerant, there will be some tendency for the refrigerant passing through the restrictor to gasify before leaving the restrlctor.

Comparing these two conditions of operation,

it will be seen that unden high load conditions, refrigerant leaves the restrlctor in a liquid state, while under low load conditions, the refrigerant leaves the restrlctor in a partly gasified condition. Inasmuch as any given fixed restrlctor will pass many times the quantity by weight of refrigerant in the liquid phase than it will pass in the gaseous phase. it will be seen that the normal relation between the rate of flow through the restrlctor and the pressure difference across the same is materially altered. Thus, for a given pressure difference across the restrlctor, the rate of flow therethrough will be greater under high load conditions than it will be under low load conditions, due to the gasication of a part of the refrigerant passing through the restrlctor under low load conditions. If this controlling effect on the rate of flow be now considered in relation to the variation of pressure differences. across the restrlctor under high and low load conditions, respectively, it will be seen that under high load conditions, the rate of flow through the restrlctor is increased by the maintenance of the refrigerant in a liquid condition throughout the restrlctor as well as by the high pressure difference across the restrlctor, whereas under low load conditions, the refrigerant is held back by the gasification of some of the refrigerant in the restrlctor, as well as by the lower pressure difference across the restrictor. It. therefore, follows that the pressure variations in the system do not need to be as great to accomplish a given amount of control over the rate of flow as are required without the use of the present invention.

In order to achieve a more gradual utilization of the controlling effect heretofore described, the evaporator may be constructed as shown in Fig. 4 in which the restrlctor 20 is mounted in a vertical position rather than in a horizontal one and has its inlet at the bottom and its outlet at the top. By the use of this construction, the rising and falling of the liquid level within the evaporator produces a more gradual effect on the refrigerant in the restrlctor than that produced by the construction of Fig. l.

While the invention has been disclosed in connection with a refrigerating apparatus which is designed to operate continuously at varying outputs throughout a substantial range, it will be understood that many of its advantages may be derived from its incorporation in refrigerators of other design. While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within4 the scope of the claims which follow.

What is claimed is as follows:

1. In a refrigerating apparatus, the combination of a compressor, a condenser, a'restrictor and an evaporator connected to form a. refrigerant circuit and proportioned tov cause variations in the level of liquid refrigerant in the evaporator with variations in load conditions, the restrlctor being in heat exchange relation with the refrigerant in the evaporator intermediate the upper and lower limits of travel of the liquid refrigerant level.

2. An evaporator for a refrigerating apparatus comprising means forming a vertically extending refrigerant chamber having a liquid refrigerant inlet and a gaseous refrigerant outlet, a restrlctor comprising a passage of relatively great length and small cross section, and having a refrigerant inlet and a refrigerant outlet, said restrlctor being mounted with at least a portion ln heat exchange relation to the refrigerant in said chamber intermediate the upper and lower limits of travel of the liquid refrigerant level therein and having its outlet in communication with the inlet to the evaporator.

3. An evaporator for a refrigerating apparatus comprising means forming a vertically extending refrigerant chamber having a liquid refrigerant inlet and a gaseous refrigerant outlet, a restrictor comprising a passage of relatively great length and small cross section, and having a refrigerant `inlet and a refrigerant outlet, said restrictor being mounted with at least a portion inside said chamber and in heat exchange relation to the refrigerant in said chamber intermediate the upper and lower limits of travel of the liquid refrigerant level therein and having its outlet in communication with the inlet to the evaporator.

4. An evaporator for refrigerators comprising a plurality of sheet like portions secured together to form a vertically extending refrigerant chamber and a restrictor comprising a passage of relatively great length and small cross section in heat exchange relation with the refrigerant in said chamber positioned to exchange heat with said refrigerant at varying rates with variations in the liquid refrigerant level in said chamber.

IE5. An evaporator for refrigerating apparatus comprising means forming a vertically extending refrigerant chamber and a fixed restrictor in heat exchange relation with the refrigerant in said chamber positioned to exchange heat with said refrigerant at varying rates with variations in the liquid refrigerant level in said chamber.

6. An evaporator for refrigerators comprising a plurality of sheet like portions .secured together to form a vertically extending refrigerant chamber and a fixed restrictor in heat exchange relation with the refrigerant in said chamber posiwvtioned to exchange heat with said refrigerant at 7. In a refrigerating apparatus, the combination of a compressor, a condenser, a restrictor and an evaporator connected to form a refrigerant circuit and proportioned to cause variations in the level of liquid refrigerant in the evaporator with variations in load conditions, the restrictor being within the evaporator in a position intermediate the maximum and minimum liquid refrigerant levels in said evaporator.

8. An evaporator for refrigerating apparatus comprising means forming a vertically extending refrigerant chamber having a liquid refrigerant inlet and a gaseous refrigerant outlet, a restrictor comprising a passage of relatively great length and small cross-section, and having a refrigerant inlet and a refrigerant outlet, said restrictor being mounted with at least a portion in heat exchange relation to the refrigerant in said chamber intermediate the upper and lower limits of travel of the liquid refrigerant level therein and having its outlet in communication with the inlet t the evaporator, said restrictor being vertically disposed whereby different portions of said restrictor are differentially cooled.

9. The method of controlling the circulation of refrigerant in a compressor-condenser-xed restrictor-evaporator refrigerating system which comprises automatically controlling the amount of gasification of the refrigerantwtaking place in. 

